Flexible barrier film structure

ABSTRACT

A barrier film for separating liquid and air, including a liquid crystalline polymer layer having a glass transition temperature less than about 115° C., and having a thickness less than about 15 microns. The barrier film further including a heat-sealable layer, and an adhesive layer interposed between the liquid crystalline polymer layer and the heat sealable layer, forming the barrier film.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application and claims the benefit andpriority of U.S. patent application Ser. No. 10/346,528 filed Jan. 17,2003 which is a continuation in part of U.S. application Ser. No.09/702,236, (abandoned) filed on Oct. 30, 2000, entitled FlexibleBarrier Film Structure.

BACKGROUND Description of the Art

Ink-jet technology is employed in hard-copy-producing devices such ascomputer printers, graphics plotters and facsimile machines. By way ofbackground, a description of ink-jet technology is provided in variousarticles in the Hewlett-Packard Journal such as those in the followingeditions: Vol. 36, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol.39, No. 5 (October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6(December 1992) and Vol. 5, No. 1 (February 1994).

Barrier films are used in several aspects of ink-jet technologyincluding to form: (1) bags for containing air for use in a pressureregulator such as that described in U.S. Pat. No. 5,975,686 to Hauck etal.; and (2) bags for containing ink, also referred to asink-containment devices, such as those described in pending U.S. patentapplication Ser. No. 08/869,446 to Olsen et al. Both of theabove-identified patent and pending patent applications are incorporatedherein by reference. For ink-containment applications, theink-containment device may be part of a disposable printer cartridge orit may be part of a so-called off-axis supply of ink.

In either of the two above-identified applications for barrier films,one of the functions of the barrier film is to provide effectiveseparation of air and ink. In the pressure regulator application, thebag actuates the pressure regulator by expanding and contracting as afunction of back pressure that exists in an ink accumulator associatedwith the pressure regulator and ambient pressure that is communicatedthrough a suitable vent formed in the pressure regulator. To function,the bag must be flexible and must exhibit effective chemical stabilityto ink or other volatile liquid writing media. If the bag is notflexible, it will not actuate the pressure regulator.

In addition, if the bag is not stable in an ink environment, it willallow air to permeate through it. When this occurs, the bag will nolonger provide for pressure regulation. To provide pressure regulation,the barrier film forming the bag must stop air from coming into the ink.If it allows air to come into the ink, then there will no longer be thedesired differential pressure that prevents many unwanted events such asvariations in print density and print quality, dripping of ink at theink-jet pen nozzle, and depriming of the print cartridge.

For ink-containment devices, the barrier film must again separate airand ink to prevent the ink from drying out as it is a volatile writingmedium. As a result, there is a continuing need to develop barrier filmsthat provide desired, long term separation of air and ink so thatink-containment devices have a correspondingly long shelf life. None ofthe known prior art ink-containment devices provides for the securecontainment of ink against the possibility of ink leakage duringlong-term storage, normal use or accidental shock or other trauma to thecontainer.

There have been many conventional proposals for barrier films and thoseproposals have included use of the following chemical compounds asbarrier layers within a composite film: (1) PVDC (polyvinylidenechloride—a DOW version is sold under the trademark SARAN and SARANEX);(2) PVDF (polyvinylidene fluoride—a commercial version is sold under thetrademark KYNAR); (3) EVOH (ethylene-vinyl alcohol copolymer); (4) metalfilms such as aluminum, silicon oxide or silicon dioxide; (5) ECTFE(ethylene chlorotrifluoroethylene copolymer); (6) PCTFE(polychlorotrifluoroethylene polymer); and CVD diamond-like coated films(where CVD refers to a chemical vapor deposition process).

For either the pressure-regulator or the ink-containment deviceapplication, the barrier film structure must exhibit the followingcharacteristics: flexibility, strength, and fluid-impermeability wherethe fluid may be ink, other printable liquid writing media, air, orother gases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, sectional view of a pressure regulator of anfluid ejection cartridge including a flexible barrier film structureaccording to an embodiment of the present invention;

FIG. 2 is an enlarged, fragmentary, sectional view of the flexiblebarrier film structure encircled by circle-2 of FIG. 1 according to anembodiment of the present invention;

FIG. 3 is a fragmentary, sectional view of an ink containment deviceassociated with an ink-jet printer according to an alternate embodimentof the present invention;

FIG. 4 is a perspective view of a fluid ejection cartridge regulatorincluding a flexible barrier film structure according to an alternateembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The flexible barrier film structure of the present invention is one foruse in devices such as for example a fluid ejection cartridge toseparate a fluid and air. The flexible film structure includes a filmbody formed of plural layers, wherein a first layer is formed as aliquid crystalline polymer (LCP), and wherein the film body exhibits aflexibility of less than about 6 grams force (gf) according toconventional film flexibility testing methods. The presently preferreduse of the invention is in a five-layer flexible film as follows:heat-sealable layer/tie layer/LCP/tie layer/heat-sealable layer. The tielayer may also be thought of as an adhesive layer.

Preferably the LCP is formed with a thickness of in the range of about5-10 microns, however in alternate embodiments a thickness less thanabout 15 microns may also be used. Each tie layer is formed with athickness in the range of about 3-10 microns, and each heat-sealablelayer is formed with a thickness in the range of about 5-15 microns.Suitable materials for the tie layer include a terpolymer sold under thetrademark LOTADER 8900, and for the heat-sealable layer include LDPE,MDPE or HDPE (low-medium- or high-density polyethylene). Flexibility ofthe overall film structure is optimized by using LDPE as well as byvarying the thickness of the LCP layer with thinner LCP layers providinggreater flexibility.

The surprising result of the invention is that LCP, a material thoughtto be unacceptably stiff for the above-described barrier filmapplications, is actually a substantially flexible material when formedin a thickness range of less than about 15 microns and more preferablywhen formed in a thickness range of 5-10 microns. In general, LCPexhibits a flexural modulus about 3-5 times higher than other polymersthat are candidates for use in barrier film applications. However,according to the present invention, suitably thin LCP layers formed inmulti-layer barrier film structure exhibit excellent flexibility andchemical stability to ink.

These and additional objects and advantages of the present inventionwill be more readily understood after consideration of the drawings andthe detailed description of the preferred embodiment which follows.Referring to FIG. 1, an exemplary embodiment of the present invention isshown as part of a pressure regulator for a fluid ejection cartridgeutilized as an ink-jet pen and is similar to the regulator described inU.S. Pat. No. 5,975,686 to Hauck et al. For purposes of thisdescription, and particularly for further details of the need for backpressure in ink-jet printers, applicant also incorporates by referencethe teachings of U.S. Pat. No. 5,736,992 to Pawloski, Jr.

Still referring to FIG. 1, flexible barrier film structure 10 is formedas a bag 12 which is located in a pressure regulator 14 which contains avolatile liquid writing medium such as ink 16. Bag 12 contains air 18and functions to provide back pressure in an amount effective to preventthe above-identified undesired effects such as dripping of ink at theink-jet pen nozzle (not shown). The presently preferred process forforming film structure 10 is by using conventional co-extrusionequipment, following the usual requirements for processing the materialprior to co-extrusion. In addition, in alternate embodiments, many otherprocesses for forming a bag made of a multi-layer film structure mayalso be utilized to form bag 12 from flexible barrier film structure 10;such as, for example, lamination.

Referring to FIG. 2, an enlarged section of flexible barrier filmstructure 10 shows that it is formed of five layers as follows: twoouter layers 10 a, two adhesive layers 10 b that each bond one of outerlayers 10 a to opposite sides of a core layer 10 c. Outer layers 10 aare made from a heat-sealable material such as low-, medium- orhigh-density polyethylene (also referred to as LDPE, MDPE and HDPE,respectively). As noted above, the flexibility of flexible barrier filmstructure 10 may be optimized by using LDPE as well as by varying thethickness of the LCP layer with thinner LCP layers providing greaterflexibility. Adhesive layers 10 b may be formed of any suitable adhesivesuch as an adhesive marketed under the trademark LOTADER 8900 by ElfAtochem Inc.

Core layer 10 c is formed of a liquid crystalline polymer such as thatmarketed under the name VECTRA by Ticona Inc. In this embodiment, theliquid crystalline polymer layer, forming core layer 10 c, is anaromatic polyester layer having recurring monomer units derived fromterephthalic acid, 6-hyrdoxy-2-naphthoic acid, p-hydroxybenzoic acid,4,4′-biphenol, and resorcinol. In this embodiment, for every 100 molesof the recurring monomer units the aromatic polyester includes 30-35moles of p-hydroxybenzoic acid units, 35-40 moles of6-hyrdoxy-2-naphthoic acid units, 15 moles of terephthalic acid units,10 moles of 4,4′-biphenol units, and 5 moles of resorcinol units. Inalternate embodiments, for every 100 moles of the recurring monomerunits the aromatic polyester includes 20-40 moles of p-hydroxybenzoicacid units, 10-40 moles of 6-hyrdoxy-2-naphthoic acid units, 15-30 molesof terephthalic acid units, 5-20 moles of 4,4′-biphenol units, and 5-20moles of resorcinol units may also be utilized. In still otherembodiments, other liquid crystalline polymers having other monomerunits may also be utilized.

The liquid crystalline polymer, forming core layer 10 c, has a glasstransition temperature in the range from about 100° C. to about 108° C.In alternate embodiments, liquid crystalline polymer layers having aglass transition temperature in the range from about 80° C. to about115° C. may also be utilized. In addition, the liquid crystallinepolymer, forming core layer 10 c, has a melt viscosity of at least 500poise, however, in alternate embodiments a liquid crystalline polymerhaving a melt viscosity of at least 300 poise, at a shear rate of 1000reciprocal seconds measured at 230° C. in a capillary rheometer using anorifice 1 mm in diameter and 30 mm long. Thus, by utilizing a core layerhaving a glass transition temperature in substantially the same range aseither the glass transition or melting temperatures of the heat sealableand tie layers, co-extrusion may be utilized to form multi-layered filmstructure 10. The co-extrusion process includes combining the liquidcrystalline polymer, the heat sealable polymer, and the adhesive polymerin a molten state in an extrusion die head and extruded through a slitto yield a multi-layered film. By utilizing a co-extrusion processthinner layers of each material may be utilized to form a thinneroverall thickness than that obtained by conventional laminationprocesses.

Still referring to the multi-layer illustration in FIG. 2, preferredthicknesses and thickness ranges for each layer is as follows: (1) eachouter layer 10 a preferably has a thickness of about 10 microns and iswithin a thickness range of about 5-15 microns; (2) each adhesive layer10 b preferably has a thickness of about 5 microns and is within thethickness range of about 3-10 microns; and (3) core layer 10 cpreferably is about 5 microns thick and is within a thickness range ofabout 5-10 microns and may be less than 15 microns thick. To maintainthe desired flexibility feature described below, it has been found thatcore layer 10 c at a thickness of less than 10 microns is optimal

Another way to characterize flexible barrier film structure 10 is tostart first with core layer 10 c and refer to it as a first layer. Next,adhesive layer 10 b could be thought of as a second layer and outerlayer 10 c could be thought of as a third layer.

The presently preferred embodiment of film structure 10 is to form it asbag 12 for use in association with a pressure regulator for an ink-jetcontainer, and to form film structure 10 in the following pattern offive layers: heat-sealable layer/adhesive layer/LCP/adhesivelayer/heat-sealable layer. Preferably, each heat-sealable layer is LDPE,each adhesive layer is LOTADER 8900 adhesive, and the LCP is the onesold under the trademark VECTRA by Ticona.

Referring to FIG. 3, another embodiment of the invention is shown asflexible barrier film structure 110 formed as a bag 112 located in acontainer 114. Bag 112 contains ink 116 and there is air 118 in thatvolume of the container that is not taken up by bag 112. Except for filmstructure 110, the construction of bag 112 such as its configuration maybe like any known ink containment bag. Likewise, container 114 may beany known associated container.

Referring to both FIGS. 1 and 3, flexible barrier film structure 10/110effectively prevents undesired air/ink interaction. In the case of thepressure regulator application shown and described in FIG. 1, filmstructure 10 stops air from coming into the ink so that the desireddifferential pressure is maintained as described above. In the case ofthe ink-containment device shown in FIG. 3, film structure 110 preventsair from entering bag 112 which would cause ink 116 to dry up. Inaddition, if air diffuses into the ink and saturates the ink, when theink is placed under negative pressure in an ink-containment device witha printhead, the air comes out of the saturated ink solution and becomestrapped within the ink delivery system to the printhead. Over time thisaccumulated trapped air displaces the ink within the ink delivery systemand prevents proper pressure regulation within the printhead.

Referring again to FIG. 2, first layer/core layer 10 c surprisinglyprovides the necessary flexibility for either application shown in FIG.1 or 3. The LCP that forms first layer 10 c exhibits a flexibility of 6gram force according to conventional film flexibility test procedures.In addition, first layer 10 c provides improved chemical stability inink or in other volatile liquid writing media. Conventional permeabilitytesting of film structure 10/110 gave consistently low values indicatingthat the film structure does not degrade in an ink environment. Forexample, following the standard oxygen permeation testing provided byMocon Corporation, superior barrier results were obtained for filmstructure 10/110 that had been soaked in ink-jet inks according to theusual test methods. Following that known testing, film structure 10/110outperformed various conventional barrier films including ones formedwith a PVDC layer using the material marketed by DOW Corporation underthe trademark SARANEX 11.

Referring to FIG. 4, an alternate embodiment of a barrier film of thepresent invention utilized in a pressure regulator is shown in aperspective view. In this embodiment, flexible bag 465 is staked tofitment 467 that is preferably press-fit into a crown which forms thebottom portion or fluid delivery portion of an inkjet cartridgecontainer. The crown and ink-jet cartridge container are made from athermoplastic polymer utilizing conventional injection moldingequipment. Fitment 467 includes vent 469 to ambient pressure in theshape of a helical, labyrinth path. Vent 469 connects to, and is influid communication with, the inside of flexible bag 465, so thatflexible bag 465 is maintained at a reference pressure. The helical pathreduces the diffusion of fluid out of the fluid container via diffusionthrough flexible bag 465. In this embodiment flexible bag 465 is formedfrom film body 10. Flexible bag 465 include first section 470, secondsection 472 and folding section 474 forming a folded structure having atleast one fold. First section 470 and second section 472 aresubstantially parallel to each other with the three sections 470-474forming a U shaped structure. Such a folded bag structure may beanalogized to a bellows like structure. As the folded sections inflatethe two sections push on each other expanding against the levers (notshown) of the regulator. In addition, as flexible bag 465 expands andcontracts (i.e. inflates and deflates) the contact area to the leversremains substantially constant, providing a substantially linearresponse to pressure changes. Cutting a sheet of flat film, having themulti-layered structure shown in FIG. 2 and described above, to thedesired size forms flexible bag 465. The flat film is staked to fitment467 and then a hole is formed in the film that mates, or fluidicallycouples, with vent 469 to allow air to pass through vent 469 to theinside of flexible bag 465. The flat film is then folded in half andstaked around the perimeter using heat and pressure applied to the outeredges of the film, forming first lung 476 and second lung 478. Firstlung 476 and second lung 478 are then folded forming a flexible foldedbag as described above. In alternate embodiments corners 480 may bestaked or tacked. Flexible bag 465 may then be inserted into an ink-jetcartridge container.

The invented system has broad applicability in connection with flexiblebarrier films for hard-copy-producing devices, and has more particularapplicability to ink-jet or other fluid controlled printers whichrequire flexible barrier films to form air bags used in association withpressure regulators and to form ink-containment devices for holding inkor other fluids in disposable printer cartridges and in off-axissupplies of ink or fluids. Air bags for use with ink-jet pressureregulators made from the flexible barrier film structure of the presentinvention have proven themselves reliably and securely to maintainseparation from air and ink, and to exhibit the flexibility required tofunction as an expandable/contractible bag that actuates the pressureregulator to maintain a desired pressure differential between backpressure that exists in an ink accumulator associated with the pressureregulator and ambient pressure. The invented system is inexpensivelymanufactured using existing tools, dies and assembly processes andequipment.

Accordingly, while the present invention has been shown and describedwith reference to the foregoing preferred embodiments, it will beapparent to those skilled in the art that other changes in form anddetail may be made therein without departing from the spirit and scopeof the invention as defined in the appended claims.

1. A method of making a flexible barrier film structure, comprising:cutting a sheet of a flat barrier film to the desired size, said flatbarrier film having a liquid crystalline polymer layer, a heat sealablelayer, and an adhesive layer interposed between said liquid crystallinepolymer layer and said heat sealable layer, said liquid crystallinepolymer layer having a glass transition temperature in the range fromabout 80° C. to about 115° C., and a thickness less than about 15microns; staking said flat barrier film to a fitment having a vent;folding said flat barrier film substantially in half forming a foldedperimeter; and staking said flat barrier film around said foldedperimeter.
 2. The method in accordance with claim 1, further comprisesforming a hole in said flat barrier film fluidically coupled to saidvent.
 3. The method in accordance with claim 1, wherein cutting saidsheet of said flat barrier film further comprises cutting a flat barrierfilm having an aromatic polyester polymer layer.
 4. The method inaccordance with claim 3, wherein cutting said flat barrier film havingsaid aromatic polyester polymer layer further comprises cutting saidaromatic polyester polymer layer having recurring monomer units derivedfrom terephthalic acid, 6-hyrdoxy-2-naphthoic acid, p-hydroxybenzoicacid, 4,4′-biphenol, and resorcinol.
 5. The method in accordance withclaim 1, further comprising: heating said liquid crystalline polymerlayer, said adhesive layer, and said heat sealable layer to a moltenstate in an extrusion die head; co-extruding said liquid crystallinepolymer layer, said adhesive layer, and said heat sealable layer througha slit; and generating a multi-layered barrier film of said liquidcrystalline polymer layer, said adhesive layer, and said heat sealablelayer.
 6. A pressure regulator including a flexible bag formed from aflexible barrier film manufactured in accordance with the method ofclaim
 5. 7. A flexible bag formed from a flexible barrier filmmanufactured in accordance with the method of claim
 5. 8. A pressureregulator including a flexible bag formed from a flexible barrier filmmanufactured in accordance with the method of claim
 1. 9. A flexible bagformed from a flexible barrier film manufactured in accordance with themethod of claim
 1. 10. The method in accordance with claim 1, whereinsaid staking said flat barrier film to a fitment having a vent, saidfolding said flat barrier film substantially in half forming a foldedperimeter, and said staking said flat barrier film around said foldedperimeter comprise forming a folded flexible bag from said flat barrierfilm, and further comprising: attaching said fitment to a crown; andinserting said crown including said folded flexible bag into an ink-jetcartridge container.
 11. A fluid ejection cartridge including a foldedflexible bag manufactured in accordance with the method of claim
 10. 12.The method in accordance with claim 1, wherein said liquid crystallinepolymer layer has a flexibility of less than about 6 grams force. 13.The method in accordance with claim 1, wherein said liquid crystallinepolymer layer has a thickness of less than about 10 microns.
 14. Themethod in accordance with claim 1, wherein said liquid crystallinepolymer layer has a glass transition temperature in the range from about100° C. to about 108° C.
 15. The method in accordance with claim 1,wherein said glass transition temperature of said liquid crystallinepolymer layer is in the same range as one of a glass transitiontemperature and a melting temperature of said heat sealable layer andsaid adhesive layer.
 16. The method in accordance with claim 1, whereinsaid heat sealable layer is selected from low-density, medium-densityand high-density polyethylene.
 17. The method in accordance with claim1, wherein said adhesive layer is a terpolymer.
 18. The method inaccordance with claim 1, wherein said liquid crystalline polymer layerhas a thickness in the range from about 5 microns to about 10 microns,said heat sealable layer has a thickness in the range from about 5microns to about 15 microns, and said adhesive layer has a thickness inthe range from about 3 microns to about 10 microns.
 19. The method inaccordance with claim 18, wherein said liquid crystalline polymer layerhas a thickness of about 5 microns, said heat sealable layer has athickness of about 10 microns, and said adhesive layer has a thicknessof about 5 microns.